Supernova appears in galaxy M101

A supernova has exploded in the galaxy M101 in the well-known constellation of Ursa Major. As of 23 May the star’s brightness is magnitude 11, so while you won’t be able to spot it as a new star just by looking up at the sky, amateur astronomers with medium-sized telescopes (say 150 mm and upwards) should be able to pick it out visually if they are accustomed to using the instrument.

Supernova SN2023ixf was discovered by Japanese amateur astronomer Koichi Itagaki on 19 May, beating professional supernova surveys. Itagaki is a prolific discoverer of such objects, and has several telescopes constantly scanning the sky for novae and supernovae, using funding from his sucessful business marketing peanuts.

M101 is one of the closest galaxies to our own Local Group of galaxies, lying just 21 million light years away. The galaxy itself is notoriously hard to spot unless you have dark skies, however, despite its closeness, because it lies face-on to us. But anyone equipped to take long-exposure images through their telescope will be able to photograph the object quite easily.

Even photographically the supernova just appears as a star, so you will need to compare the view with a map or photograph to be able to pick it out. Photographs taken by members are shown in the Gallery below.

To find the galaxy visually, first locate the stars Mizar and Alkaid – the two stars at the end of the ‘handle’ of the Plough or the tail of the Great Bear, which is almost overhead at this time of year. Then use the map below to hop from star to star to locate M101, using the line of stars stretching from Mizar. If you have a Go To telescope this should find the area of the galaxy directly, but don’t expect the galaxy to jump out at you. It is quite large and faint. The large circle shows a 5° field of view, typical of binoculars or a telescope finder scope.

The rectangular box shows the area of sky magnified in the lower view, with a photograph of the galaxy superimposed. In this case the circle shows a 1° field of view typical of a low-power eyepiece on a telescope. Even if you can’t see the galaxy, you may be able to pick out the supernova, which is shown by the small circle. The supernova outshines all the other stars of the galaxy put together.

The object is likely to fade slowly, and should remain visible in amateur telescopes for some weeks.

M101 finder
Location of M101 compared with Mizar and Alkaid in Ursa Major. Map compiled using Chris Marriott’s SkyMap.
M101 mag13
Detailed view of the area of M101, showing stars to magnitude 13.5. Photo by David Davies superimposed on map. The white circle shows a field of view of 1°. Click to enlarge.


sn in m101_AS
Photo by Andy Smith taken 20 May 2023 using Canon 90D DSLR camera through Orion Optics 300 mm telescope with L-Pro Max filter. He stacked 20 three-minute exposures.
Photo by David Davies, taken 22–23 May 2023, using 250mm Ritchey-Chrétien reflector with 0.7x reducer and ZWO ASI294MC camera. A combination of 35 two-minute exposures. David reports that an exposure time as short as 30 seconds will reveal the supernova well.